a) Field of the Invention
The present invention relates to communication techniques, and more particularly to communication techniques for establishing synchronization among a plurality of communication apparatuses.
b) Description of the Related Art
Digital serial communication of IEEE 1394 standards is prevailing. By using IEEE 1394 standards, a network interconnecting a plurality of communication nodes can be configured. For example, one reception node can receive audio data from a plurality of transmission nodes.
Consider the case wherein first and second transmission nodes transmit data to one reception node at the same time. In this case, the time when data from the first transmission node is received at the reception node is often different from the time when data from the second transmission node is received, because of a difference of distance between nodes or because of some other reasons. For example, the reception node receives the data from the first transmission node and thereafter receives the data from the second transmission node.
Transmission and reception nodes have cycle timers specific to them. The cycle timers are not in synchronization with each other. It is difficult for a reception node to synchronize the data from a first transmission node with the data from a second transmission node.
There is another case wherein one transmission node transmits the same data to first and second reception nodes approximately at the same time. However, similar to the above-described case, the time when the first reception node receives the data is often different from the time when the second reception node receives the data. Since the first and second reception nodes reproduce the received data by using their own cycle timers, the reception processes at the first and second reception nodes are likely to have timing shifts. It is difficult for a reception node to synchronize data transmitted from a plurality of transmission nodes. It is also difficult for a transmission node to synchronize data to be transmitted to a plurality of reception nodes.